> ## Content Index > Fetch the complete content index at: https://www.spotedcrypto.com/llms.txt > Use this file to discover other available public pages before exploring further. # Layer 2 vs Layer 3 in Crypto: How L3 Appchains Differ From Rollups - URL: https://www.spotedcrypto.com/layer-2-vs-layer-3-blockchain-l3-appchains-explained/ - Published: 2026-11-06T01:13:03.000Z - Updated: 2026-11-06T03:44:01.000Z - Description: How Ethereum L2 rollups differ from L3 appchains, what Vitalik's 2022 argument allows, and how teams choose between them. - Author: Sungjae Lee - Tags: Ethereum, Guides, hash-en, layer-2, layer 3, rollups, appchains, Arbitrum, scaling, English In September 2022, Vitalik Buterin warned that stacking the same rollup design on top of itself does not multiply scaling. Four years later, Ethereum has hundreds of chains built on it, and traders and builders still have to work out what each extra "layer" actually gives them. ## What Is the Difference Between a Layer 2 and a Layer 3 Blockchain? A Layer 2 (L2) is a blockchain that settles to Ethereum (Layer 1) and inherits its security. A Layer 3 (L3) is usually an app-specific chain that settles to an L2 instead of to Ethereum directly. It inherits the L2's security and adds its own custom execution . According to [ethereum.org](https://ethereum.org/en/layer-2/?ref=spotedcrypto.com), an average transaction costs about $0.025 on Ethereum mainnet and about $0.0017 on L2s . For most users, the move from L1 to L2 is where the big cost savings happen. An L3 is a choice about customization, not a third round of the same savings. **Quick Answer:** An L2 settles directly to Ethereum. An L3 is an app-specific chain that settles to an L2, which lets it have custom execution, its own gas token and its own throughput. L2s already cut average fees from about $0.025 on mainnet to about $0.0017 (ethereum.org, November 2026). An extra layer is mainly worth it when an app needs its own environment. The working test for an L2 is where it stores its data. Per [ethereum.org](https://ethereum.org/en/layer-2/?ref=spotedcrypto.com), networks that post their transaction data to Ethereum mainnet are rollups, the true extensions of Ethereum . An L3 works one level higher. Each L3 runs its own sequencer and posts compressed state roots to a smart contract on an L2\. Its transaction data can live on that L2, on Ethereum, or with a data-availability provider such as EigenDA . The extra hop has a cost. Leaving an L3 means two bridge steps (L3 → L2 → L1). If the L3 sits on an optimistic L2, a fully trustless exit can take up to about 14 days without a liquidity provider, according to [Eco](https://eco.com/support/en/articles/10080504-what-is-a-layer-3-l3-blockchain?ref=spotedcrypto.com) . A **sidechain** is different from both. It is a separate chain with its own consensus that connects to the main chain, Polygon PoS being the usual example, and purists do not count it as a true L2 (video: CoinGecko). | Layer type | Where it settles | Who secures it | Data location | Typical exit path | Best for | | ---------------------------------- | --------------------- | ----------------------------------------------------------- | ----------------------------------------- | ----------------------------------------------------------------- | -------------------------------------------------------------- | | L1 (Ethereum) | Itself | Ethereum validators | Ethereum mainnet | None needed | Final settlement, high-value transfers | | L2 rollup (Base, Arbitrum One) | Ethereum L1 | Inherits Ethereum security through fraud or validity proofs | Ethereum mainnet | L2 → L1; about 7 days on optimistic rollups, faster on ZK rollups | General DeFi and trading with low fees | | L3 appchain (Arbitrum chains, Xai) | An L2 | Inherits L2 security, plus its own sequencer | The L2, Ethereum, or an external DA layer | L3 → L2 → L1; up to about 14 days if trustless | Single apps needing a custom gas token, fast blocks or privacy | | Sidechain (Polygon PoS) | Itself, bridged to L1 | Its own validator set and consensus | The sidechain itself | Bridge back to L1, trusting the sidechain | Cheap throughput where you accept separate trust | The optimistic-rollup exit window in the table comes from the fraud-proof model: transactions are treated as valid unless someone challenges them, which gives a challenge period of about 7 days. ZK rollups such as Starknet and zkSync prove validity upfront instead, per [KuCoin Learn](https://www.kucoin.com/learn/crypto/layer-2-vs-layer-3-blockchains?ref=spotedcrypto.com) . Buterin's own case for L3s rests on the same logic. In his [17 September 2022 post](https://vitalik.eth.limo/general/2022/09/17/layer%5F3.html?ref=spotedcrypto.com), he wrote that "data can be compressed once, but it cannot be compressed again" . One warning before going further: "Layer 3" is not a standard term across crypto. In Ethereum it means a chain that settles on an L2\. In Michael Saylor's Bitcoin model, L3 means custodial platforms such as exchanges (video: Lex Clips). This guide uses the Ethereum meaning throughout and covers the Bitcoin meaning in its own section near the end. ## How Do Layer 0, Layer 1, Layer 2 and Sidechains Fit Together? The crypto layer stack runs from interoperability at the bottom to execution at the top. Layer 0 links chains together. Layer 1 records transactions directly. Layer 2 processes transactions off the main chain but borrows the main chain's security. A sidechain is a separate chain with its own consensus that connects to a main chain, so it sits beside the stack rather than inside it (video: CoinGecko). When you see a project label itself "L2" or "L3", you are really asking one question: whose security does it use? Each layer answers that question differently, and that answer matters more than the label when you choose where to keep funds or deploy capital. Here is each layer in one line, as summarized in [CoinGecko's explainer on Layer 0, 1 and 2](https://www.youtube.com/watch?v=LorgQfXpuK0&ref=spotedcrypto.com): - **Layer 0:** Infrastructure that lets separate Layer 1 chains interoperate and pass messages. Polkadot is the usual example (video: CoinGecko). - **Layer 1:** A base blockchain that records transactions directly on its own main chain and secures them with its own consensus. Bitcoin, Ethereum and Solana are examples (video: CoinGecko). - **Layer 2:** A network that processes transactions off the main chain and still relies on the Layer 1 for security and final settlement (video: CoinGecko). - **Sidechain:** An independent chain connected to a main chain by a bridge but running its own consensus. Polygon PoS is the common example. Purists do not count sidechains as true L2s, because a sidechain's security depends on its own validators, not on the L1 (video: CoinGecko). The line between a real L2 and a sidechain matters for traders. If a sidechain's validator set fails or colludes, Ethereum's security does not protect your funds. A rollup is designed so that Ethereum itself can enforce the correct state, even if the rollup operator goes offline or acts against users. The cleanest test comes from [ethereum.org's Layer 2 page](https://ethereum.org/en/layer-2/?ref=spotedcrypto.com): does the network store its transaction data on Ethereum mainnet? If it does, it is a rollup, which ethereum.org calls a true extension of Ethereum . If the data lives somewhere else, such as a separate committee or an outside data-availability network, users take on extra trust assumptions, however the project brands itself. The same page notes that hundreds of chains are now built on Ethereum , so the test has real practical use when you sort through them. A quick checklist for any network that calls itself a "Layer 2": 1. Does it post its transaction data to Ethereum mainnet? If yes, it is a rollup. 2. Does it run its own consensus with its own validators? If yes, it is closer to a sidechain. 3. Can you withdraw to Ethereum without the operator's permission? If not, treat its security as weaker than Ethereum's. Layer 3s carry this logic one step higher. They use the same data-and-settlement test, but they settle to an L2 instead of to Ethereum directly. ## How Do Ethereum Layer 2 Rollups Work, and Which Ones Matter in 2026? Ethereum Layer 2 rollups bundle many transactions off-chain, run them, and post the data back to Ethereum mainnet. That lets them inherit Ethereum's security at a fraction of the cost. ethereum.org puts an average L2 transaction at about $0.0017, against about $0.025 on mainnet (source: [ethereum.org, 2026-11](https://ethereum.org/en/layer-2/?ref=spotedcrypto.com)). For traders, the main difference between rollups is how each one proves its transactions are valid. That choice decides how fast you can withdraw to Ethereum without trusting anyone. There are two rollup families, and they handle proof in opposite ways: - **Optimistic rollups** (Arbitrum, Optimism's OP Stack, Base) treat every batch as valid unless someone challenges it with a fraud proof. That challenge period is why a trustless withdrawal to Ethereum takes about 7 days . Third-party bridges and liquidity providers can shorten the wait, but that means trusting them. - **ZK rollups** (Starknet, zkSync) post a validity proof with each batch. The proof is a cryptographic check that the state change is correct, so the transactions are verified upfront instead of after a dispute window (source: [KuCoin Learn](https://www.kucoin.com/learn/crypto/layer-2-vs-layer-3-blockchains?ref=spotedcrypto.com)). In practice, this means a withdrawal from Base or Arbitrum through the native bridge is slow but needs no trust in an intermediary. A ZK rollup's native exit is limited by how fast it produces and verifies proofs, not by a fixed challenge window. Both families meet the test from the previous section: they post their transaction data to Ethereum. Value on L2s is concentrated in a few chains. ETHBEAT, the site that l2beat.com now redirects to, tracks 95 projects. Of those, 22 are rollups, 3 are validiums or optimiums, and 70 fall into its "others" category (source: [ETHBEAT scaling summary, 2026-11](https://ethbeat.org/scaling/summary?ref=spotedcrypto.com)). By value secured, the top five are: 1. **Base**: about $14.12B 2. **Arbitrum One**: about $9.35B 3. **OP Mainnet**: about $1.48B 4. **Mantle**: about $1.21B 5. **Lighter**: about $1.05B Base and Arbitrum One alone account for about $23.5B. That is roughly six times the next three chains combined. The summary page does not show an aggregate total for the whole sector. For a sector-wide figure, a CEX.IO explainer says more than $42B was locked in L2s in 2025 (video: CEX.IO). This is a secondary-source estimate, not a measured on-chain total. Use it for rough scale, not for exact comparisons. Ethereum also changed at the protocol level to support this. The Fusaka upgrade went live in December 2025 and introduced PeerDAS (Peer Data Availability Sampling). With PeerDAS, nodes check that rollup data is available by sampling pieces of it instead of downloading all of it. This improves how L2s use Ethereum's data availability (source: [ethereum.org](https://ethereum.org/en/layer-2/?ref=spotedcrypto.com)). Because data posting is a rollup's biggest running cost, more data capacity on Ethereum is the main reason L2 fees stay in fractions of a cent. ethereum.org says that with hundreds of chains now built on it, Ethereum has become "more cost-effective, faster, and accessible." For a retail trader picking a chain, three questions matter most: - **Proof type:** optimistic or ZK. This sets how long a native withdrawal takes. - **Value secured:** how much capital sits on the chain. This affects liquidity depth and slippage. - **Data posting:** whether the chain posts its data to Ethereum. This separates true rollups from validiums and the "others" category. These same questions become harder one layer up, where appchains settle to an L2 instead of to Ethereum. ## What Did Vitalik Actually Say About Layer 3s? Vitalik Buterin said that putting the same rollup design on top of itself again does not multiply scaling. In a post published on 17 September 2022, he argued that a third layer is worth building only for specialization: privacy, scaling tuned to one application, or designs that trade some trust for lower cost . The idea of rollups on rollups on rollups, each adding more throughput, does not hold up, because the main gain from a rollup can only be captured once. This is the answer to the title's "So": L3s are for *doing something different*, not for adding more of the same capacity (source: [Vitalik Buterin, 2022-09](https://vitalik.eth.limo/general/2022/09/17/layer%5F3.html?ref=spotedcrypto.com)). His argument starts with data compression. A rollup saves money mostly by compressing transaction data before posting it to the layer below. Once that data is compressed, running the same compression on it again gains almost nothing. A rollup on top of a rollup still has to post its data somewhere, and that data is already about as small as it can get. > "Data can be compressed once, but it cannot be compressed again," — Vitalik Buterin, co-founder of Ethereum (source: [vitalik.eth.limo](https://vitalik.eth.limo/general/2022/09/17/layer%5F3.html?ref=spotedcrypto.com)) From this he drew a direct conclusion. In his words, "a three-layer scaling architecture that consists of stacking the same scaling scheme on top of itself generally does not work well" . Think of it this way: if an L2 cuts costs by some factor, an identical L3 on top does not cut them by the same factor again. The second layer mostly adds overhead, an extra bridge hop and an extra place for things to go wrong. He did not reject L3s outright. He named three cases where a third layer makes sense, because each one adds something the L2 below does not already provide : - **Specialized functionality.** The L3 offers features the base L2 does not, with privacy as his main example. The L2 handles general scaling and the L3 adds a different execution model on top. - **Customized scaling for specific applications.** One application, such as a game or a high-frequency trading venue, gets its own execution environment with rules, fees and throughput set for its workload instead of sharing blockspace with everyone else. - **Weaker-trust scaling.** Validiums sit on top of L2 rollups and keep data off-chain to save cost, accepting weaker guarantees in return. In this setup the layers differ by trust model, not just by number. All three follow the same rule: the upper layer has to differ in *kind* from the layer below. If the L3 is just a copy of the L2 one level up, the post's reasoning says it adds cost and complexity without adding meaningful capacity. He also suggested an alternative that may beat L3s for some uses: **proof aggregation**. This means combining proofs from many chains or many batches into one proof that is checked once, so verification costs are shared instead of each chain paying separately . A team that wants cheaper settlement, rather than a custom execution environment, may get more from aggregation than from launching another layer. For traders and builders, the practical filter is simple. When a project pitches an L3 as "more scaling," ask what it does that its parent L2 cannot: privacy, a custom gas token, app-specific throughput or a different trust model. If it has no clear answer, Buterin's 2022 reasoning suggests the extra layer mainly adds bridge risk and splits liquidity. Most of the L3 frameworks that followed were built as specialization tools, not as throughput multipliers. ## How Do L3 Appchains Work, and What Frameworks Do Teams Use? An L3 appchain is a blockchain built for one application that settles to a Layer 2 instead of to Ethereum. It works like a small rollup that treats its parent L2 as its base layer. According to [Eco's L3 explainer](https://eco.com/support/en/articles/10080504-what-is-a-layer-3-l3-blockchain?ref=spotedcrypto.com), an L3 inherits the L2's security but uses its own custom execution . For a trader, this means the chain's speed, fees and gas token are set by the app team. Its final security still runs through two settlement layers: the L2 first, then Ethereum. Most L3s work through three parts, as [Eco](https://eco.com/support/en/articles/10080504-what-is-a-layer-3-l3-blockchain?ref=spotedcrypto.com) describes them : - **Its own sequencer.** A sequencer is the node that orders transactions and produces blocks. Each L3 runs a separate one, so its block times and fee rules don't depend on how busy the parent L2 is. - **State roots posted to the L2.** The L3 regularly posts compressed state roots to a smart contract on its parent L2\. A state root is a cryptographic summary of the chain's balances. Fraud proofs or validity proofs are checked against these commitments. - **A choice of data availability.** Transaction data can go on the L2, on Ethereum, or to an outside data-availability (DA) provider such as EigenDA. This choice largely decides both cost and trust. Data posted to Ethereum or the L2 can be checked by anyone. An outside DA provider is cheaper, but users have to trust that layer as well. The data-availability choice ties back to Buterin's argument. Because data "can be compressed once, but it cannot be compressed again," an L3 that posts all its data to the L2 gets few extra savings. The cost advantage comes from *where* the data goes and how the chain is specialized, not from stacking more layers. The most widely documented L3 framework is **Arbitrum chains**, formerly branded Arbitrum Orbit. According to the [Arbitrum documentation](https://docs.arbitrum.io/launch-arbitrum-chain/a-gentle-introduction?ref=spotedcrypto.com), these chains run on the same Nitro codebase as Arbitrum One. Teams can set the following : - **Block time:** as low as 100 ms, with a 250 ms default. - **Gas token:** a custom ERC-20 instead of ETH. Gaming and community chains often use this. - **Data availability:** Rollup mode (data on the parent chain), AnyTrust (a data committee holds the data, which is cheaper but adds trust assumptions), or an external DA layer. - **Validation:** permissioned (a known set of validators) or permissionless (anyone can challenge state). Teams outside the Arbitrum ecosystem usually choose one of three other stacks, which [KuCoin Learn](https://www.kucoin.com/learn/crypto/layer-2-vs-layer-3-blockchains?ref=spotedcrypto.com) covers : - **OP Stack:** the optimistic-rollup codebase behind OP Mainnet and Base. Chains built on it rely on fraud proofs and a challenge window, and settle to an OP Stack L2 or to Ethereum. - **zkSync ZK Stack:** a validity-proof framework. Each block comes with a ZK proof, so the chain doesn't need a multi-day challenge window like optimistic designs. In return, proving takes more computing power. - **Starknet appchains:** app-specific chains built on Starknet's STARK-proof technology and Cairo environment. Teams use them when they need high throughput for heavy workloads. In practice, which framework a team picks says more than the "L3" label. Two settings tell you most of what you need: the proof system (optimistic or ZK), which sets how long withdrawals take, and the DA mode, which sets who you have to trust for your data. An Arbitrum chain in AnyTrust mode with permissioned validators is a very different risk than a ZK Stack chain that posts all its data to Ethereum, even if both are marketed as appchains. Before you bridge funds to any L3, check its documentation or ecosystem page for these two settings. ## What Are the Real Trade-Offs of Building on an L3 in 2026? The main costs of building on an L3 in 2026 are slower exits, split liquidity and weak staying power. Leaving an L3 takes two bridge hops, L3 to L2 and then L2 to Ethereum. If the L3 sits on an optimistic L2, a fully trustless withdrawal can take up to about 14 days without a liquidity provider, according to [Eco](https://eco.com/support/en/articles/10080504-what-is-a-layer-3-l3-blockchain?ref=spotedcrypto.com) . For a trader, that means capital on an L3 is harder to move than capital on an L2\. An appchain's custom execution only pays off if the app really needs it. The exit delay comes from stacking. Each hop has its own settlement rules, and on optimistic designs each hop can carry its own challenge window. Liquidity providers can front you the funds on the destination chain for a fee, but then you depend on that provider's capacity and pricing. In a fast market, when many users try to leave at once, both can get worse. Before you bridge size onto any L3, find out which exit you would actually use: the trustless route or a paid fast bridge. The second cost is fragmentation. Every new chain splits liquidity into another pool. Contracts on different L3s also cannot call each other synchronously, which means a single transaction cannot combine actions across two L3s the way it can within one chain . In practice: - **Thinner order books:** a DEX on an L3 competes for liquidity with the same assets on its parent L2, so spreads and slippage are often wider. - **No atomic composability:** a strategy that touches lending on one L3 and a swap on another has to run as separate steps, with bridge risk between them. - **More bridge exposure:** each extra hop adds another contract set and another operator you have to trust. The third cost is durability, and the record so far is mixed. Eco's September 2026 snapshot of known L3s reads less like a growth chart and more like a survival list : - **Xai** (gaming, settles on Arbitrum): live, but with only about $7.4K in DeFi TVL. - **Degen Chain** (an L3 on Base): marked as sunsetting, with a shutdown date of 31 August 2026. - **Sanko Chain:** archived. Compare that with the parent layer. Base secures about $14.12B and Arbitrum One about $9.35B, according to [ETHBEAT](https://ethbeat.org/scaling/summary?ref=spotedcrypto.com) . An appchain with five-figure DeFi TVL that settles on a chain securing billions shows where users and capital actually are. When an L3 shuts down, users have to withdraw before the deadline, and late exits through a two-hop path can be slow and costly. None of this means L3s are a mistake. It means they fit a narrow set of uses. [KuCoin's comparison guide](https://www.kucoin.com/learn/crypto/layer-2-vs-layer-3-blockchains?ref=spotedcrypto.com) and Eco both describe the same pattern: L3s make sense when an app needs its own execution environment, its own gas token or dedicated throughput, but many have struggled to keep enough activity to justify running a separate chain . For traders, the working rule is to treat L3 balances as operating capital, not storage. Keep only what the app needs, know your exit route ahead of time, and watch for sunset notices. ## Should You Use an L2, Launch an L3, or Use a Shared Rollup? A Decision Framework For most apps and most traders, an existing Layer 2 is the best default. Launch an L3 appchain only if your app needs something a shared rollup can't give it: its own gas token, its own block times, or specialized execution such as privacy. Vitalik Buterin argued that stacking the same rollup scheme on top of itself "generally does not work well" . So an L3 has to earn its place by doing something different from the L2 below it, not by repeating it. Six criteria decide most cases. Answer them in order. If your answer to the first three is "no", a shared L2 is almost always the right call. - **Custom gas token:** Do users need to pay fees in your app's own ERC-20? Arbitrum chains support this directly . - **Throughput or latency targets:** Do you need blocks faster than a shared chain offers? Arbitrum chains can be set as low as 100 ms, against a 250 ms default . - **Privacy or specialized execution:** Does the app need logic or a virtual machine that a general-purpose L2 won't run? - **Data-availability cost tolerance:** Will you pay for rollup-grade data on Ethereum, or accept an AnyTrust or external DA provider to cut costs? - **Exit-time tolerance:** Can your users live with a trustless exit of up to about 14 days when the L3 sits on an optimistic L2? - **Composability:** Do your contracts need to call existing DeFi pools synchronously? If yes, stay on the L2 where that liquidity already sits. | Scenario | Recommended option | Vitalik's matching L3 use | Main risk | | ------------------------------------------------------------------ | -------------------------------------------------- | ---------------------------------------------- | --------------------------------------------------- | | DeFi protocol that relies on existing lending and DEX liquidity | Deploy on an existing L2 (e.g. Base, Arbitrum One) | None. No L3 needed. | Fee spikes and competition for shared blockspace | | Game or social app needing sub-250 ms blocks and its own gas token | Launch an L3 appchain | Customized scaling for specific applications | Low activity, thin liquidity, sunset risk | | App needing confidential transactions or a non-standard VM | Launch a specialized L3 | Specialized functionality (privacy) | Small user base and an extra layer of audit surface | | High-volume, low-value activity where data cost dominates | Validium-style L3 with off-chain DA | Weaker-trust designs (validiums on L2 rollups) | Data withholding by the DA committee or provider | **App builders** should start on a shared L2 and move to an L3 only once real usage shows a bottleneck. Buterin also pointed to proof aggregation as a possibly better alternative to stacking , so treat a dedicated chain as a cost you keep paying, not as a launch milestone. **Traders** should keep their main balances where the value is. Base secures about $14.12B and Arbitrum One about $9.35B , and the average L2 transaction costs about $0.0017 . Bridge to an L3 only to use a specific app. **Long-term holders** of appchain tokens should treat the token's value as tied to whether the chain stays active. Xai was live with only about $7.4K in DeFi TVL, and Degen Chain was set to sunset on 31 August 2026 . Weigh chain usage as heavily as token supply schedules. **Checklist before bridging to an L3:** 1. **Exit window:** Is the parent L2 optimistic or ZK? How many hops (L3 → L2 → L1) does a withdrawal take, and is a liquidity provider available? 2. **Remaining TVL:** Is there enough DeFi liquidity to exit a position without heavy slippage? Check on [ETHBEAT](https://ethbeat.org/scaling/summary?ref=spotedcrypto.com) or the chain's own explorer. 3. **Sequencer status:** Is the sequencer run by a single operator, and is validation permissioned or permissionless? (Arbitrum chain operators choose this; see the [Arbitrum docs](https://docs.arbitrum.io/launch-arbitrum-chain/a-gentle-introduction?ref=spotedcrypto.com).) 4. **Sunset risk:** Look for sunset or archive notices, falling activity and quiet team channels. [Eco's L3 tracker](https://eco.com/support/en/articles/10080504-what-is-a-layer-3-l3-blockchain?ref=spotedcrypto.com) already lists chains that are sunsetting or archived. ## Why Does 'Layer 3' Mean Something Different in Bitcoin? In Bitcoin, "Layer 3" usually means custodial services, not chains. The best-known version of this comes from Michael Saylor, who sorts Bitcoin into layers by who holds the coins rather than by where transactions settle. In his model, L3 covers custodial platforms such as Binance, Coinbase and Cash App (video: Lex Clips). So an "L3" in a Bitcoin conversation is a company that holds your BTC. An "L3" in an Ethereum conversation is a chain that settles to an L2. Saylor's full stack, as he describes it in a [Lex Fridman interview clip](https://www.youtube.com/watch?v=JXdT9lQgf%5FY&ref=spotedcrypto.com): - **L1, settlement:** about 350,000 transactions per day or fewer, roughly 100 million per year. It can move any amount in minutes for a few dollars in fees . - **L2, non-custodial:** open and permissionless, with BTC as gas. Lightning is his example. He claims it can reach about 350 million transactions per day, settling in seconds for fractions of a penny . - **L3, custodial:** exchanges and apps where BTC moves between accounts in milliseconds at no cost . - **"Layer 4," proprietary wrappers:** products such as GBTC shares or MSTR stock, which can't be withdrawn as BTC . Saylor also pointed out that Cash App allowed BTC withdrawals while PayPal and Robinhood at first did not. That gap caused an uproar in the community. It shows why the line between L3 and "L4" matters to holders (video: Lex Clips). The fee figures are also only claims. A [CEX.IO explainer](https://www.youtube.com/watch?v=35FF4PP58%5FA&ref=spotedcrypto.com) says Lightning can cut a Bitcoin fee from about $2.80 to about $0.001 (video: CEX.IO). Both these numbers and Saylor's throughput figures come from the speakers themselves. No one has verified them independently. Use them as rough scale, not as benchmarks. The wider point is that "Layer 3" has no standard meaning. Some general guides, including [KuCoin's L2 vs L3 explainer](https://www.kucoin.com/learn/crypto/layer-2-vs-layer-3-blockchains?ref=spotedcrypto.com), use it loosely for the application layer where dApps and users sit. They also admit that the labels overlap for custom rollups and appchains . **Takeaway:** When someone pitches an "L3," ask two questions. Where does it settle, and who holds the keys? If it settles to an L2, it is an Ethereum-style L3, and the exit, liquidity and sunset checks in this guide apply. If someone else holds your coins, it is a custodial L3 in Saylor's sense, and your main risk is whether you can withdraw. ## Frequently Asked Questions ### Is Layer 3 better than Layer 2? No, a Layer 3 is not better than a Layer 2 in every case. It is a trade-off. An L3 lets a team pick its own gas token, block time and features such as privacy. Arbitrum chains, for example, can set block times as low as 100 ms . In return, users get slower exits and liquidity split across more chains. Most value still sits on L2s. Base secures about $14.12B and Arbitrum One about $9.35B, according to [ETHBEAT](https://ethbeat.org/scaling/summary?ref=spotedcrypto.com) . Most traders and most apps are better served on an established L2. ### What is the difference between a rollup and an appchain? A rollup is a chain that stores its transaction data on Ethereum mainnet and inherits Ethereum's security. [ethereum.org](https://ethereum.org/en/layer-2/?ref=spotedcrypto.com) treats this data test as what makes a network a true extension of Ethereum. An appchain is a chain built for one application. It can be a rollup, an L3 that settles to an L2, or a sovereign chain with its own consensus. The two labels describe different things: a rollup is defined by where its data and security come from, and an appchain by what it is for. They overlap for custom rollups, so check where a chain settles rather than relying on the name, as [KuCoin Learn](https://www.kucoin.com/learn/crypto/layer-2-vs-layer-3-blockchains?ref=spotedcrypto.com) notes. ### How long does it take to withdraw from an L3 to Ethereum? Leaving an L3 takes two bridge hops: first from the L3 to the L2, then from the L2 to Ethereum. If the L3 sits on an optimistic L2, a fully trustless exit can take up to about 14 days without a liquidity provider, according to [Eco](https://eco.com/support/en/articles/10080504-what-is-a-layer-3-l3-blockchain?ref=spotedcrypto.com) . Fast bridges and liquidity providers can cut that to minutes. You pay a fee for this, and you take on the provider's counterparty risk. ### Did Vitalik say Layer 3s are useless? No. In his [17 September 2022 post](https://vitalik.eth.limo/general/2022/09/17/layer%5F3.html?ref=spotedcrypto.com), Vitalik Buterin argued that stacking the same rollup scheme on top of itself does not give exponential scaling, because "data can be compressed once, but it cannot be compressed again" . In the same post he named three L3 uses that do make sense: - specialized functionality, such as privacy - customized scaling for specific applications - weaker-trust designs, such as validiums on top of L2 rollups He also suggested proof aggregation as a possibly better alternative. ### What does Layer 3 mean in Bitcoin? In Michael Saylor's Bitcoin model, Layer 3 means custodial platforms such as Binance, Coinbase and Cash App, where someone else holds your BTC (video: Lex Clips). In that model, Layer 1 is the Bitcoin base chain and Layer 2 is a non-custodial protocol such as Lightning. This is a different meaning from Ethereum, where an L3 is a chain that settles to an L2\. For Bitcoin users, the main question about an L3 is whether the platform lets you withdraw your coins. Enjoyed this article? Subscribe to get new stories by email whenever they're published. [Subscribe](#/portal/signup)